Unsaturated esters and polymers thereof



I Patented o r, 2, 1945 unsn'ruasran as'rans mamas Tunas-F a Irving E. Muskat, Akron, and Franklin Strain,

Norton Center, Ohio, asslgnors to Pittsburgh Plate Glass Company, Pittsburgh, Pa., a corpo- -ra tion of Pennsylvania No Drawing. Application mm. '2, 1942, I Serial m suse mm. (01. zoo-1a) This invention relates to a new class of unsaturated esters of unusual properties which render them valuable in various chemical arts. 1

The present case is acontinuation-in-part of Serial No. 361,280, filed October 15, 1940, by Irving E. Muskat and Franklin Strain.

Because of the indefinite scope and variation in the common usage of certain chemical expressions, it is necessary to deilne and limit such expressions which are used in the following specification and claims.

The term "polyhydroxy compound" is intended to include all compounds having two or more hydroxy groups and which do not contain any free acid roups. These polyhydroxy compounds may have ether, thioether, amino, amido, or ester linkages between the reactive hydroxy groups. By ester linkage we mean a linking oxygen atom derived by inter-reaction of an alcohol group and an acid group. Thus, a carbonate contains two ester linkages.

By simple polyhydroxy compounds we mean polyhydroxy compounds which do not contain gro ps such as resorcinol, ethylene glycol, glycerine, etc. Polyhydroxy ethers such as diethylene glycol, tripropylene glycol, and the corresponding thioethers are considered .to be simple poly-hydroxy compounds. The polyhydroxy compounds which contain ester linkages between the reactive hydroxy groups such as ethylene glycol mono lactate hols, having up to ten carbon atoms may be used, such as esters of cinnamyl alcohol, phenyl pro.- pargyl alcohol; p-allyl ethynyl carbinol, geraniol, linalool, or p-isobutyl allyl alcohol.

The new esters are the polyesters of the simple polyhydroxy compounds including the glycols such as ethylene g ycol, propylene'glycol or other ,2 alkylene glycol, trimethylene .giycol, 1,4- butylene glycol, pentamethylene glycol, alpha methyl pentamethylene glycol, or methyl ether of glycerol, the polyglycols such as (11-, tri-, or tetraethylene glycol, di-, tri-, or tetrapropylene glycol or the corresponding polyglycerols, the higher polyhydroxy alkanes, such as glycerol, glycerol monochlorhy'drin, pentaerythritol, glycerol monoacetate, erythrose, pinacol, xylose, cellulose, or partial esters or ethers thereof such-as cellulose monoor dlacetate or the monoor diethyl ether oi cellulose, cellulose monocrotonate, cellulose monoor dibutyrate, polyvinyl alcohol, dextrose, lactose,orsucrose, and the cyclic polyhydroxy compounds such as quinol, hydroquinone, resorcinol, pyrogallol, hydroxy quinol, naphthaquinone, tetra-, penta, and hexahydroxy benzenes, orcinol, 1,3-xylyl alcohol or catechol. est r linkages between the reactive hydroxy I A preferred group of these esters are those in which all or at least two of the hydroxy groups of a polyhydroxy compound are esterifled with the half ester of carbonic acid and unsaturated alcohol. These neutral esters may be'represented by the general formula:

or castor oil are not considered to be within the scope of the term simple polyhydroxy compoun "due to the presence of one or more ester linkages between the 'hydroxy' groups in such compounds. 1

The invention is particularly directed to esters of unsaturated alcohols having up to five carbon atoms in the molecule such as allyl, 'methallyl,

in which R1 is the radical derived from an unsaturated alcohol and a: is a small whole number greater than one and less than four. These esters contain the radical of only a single. molecule of thepolyhydroxy compound and contain iour' ester linkages between a pair of alcohol radicals.

The carbonate esters herein contemplated may of'phosgene with alcohol, preferably at or,

about 0 C.. v v

The reaction to form the ester is preferably conducted in the presence of a suitable alkaline agent such as pyridine, sodium or potassium hydroxidel bicarbonate, or carbonate, calcium, barium, strontium, or magnesium hydroxide, oxide, bicarbonate or carbonate or other agent capable of removing H01 which is formed during the reaction. This esterification may be conducted in the presence of aqueous or non-aqueous diluents or solvents such as acetone, dioxane, benzene, chloroform, etc.

The present application is especially directed to the esters of polyhydroxy alicyclic compounds such as resorcinol, 'hydroquinone, pyrogallol, naphthaquinol, or other polyhydroxy benzenes, anthracenes, naphthalenes, phthalyl alcohol, polyhydroxy cyclopentanes, polyhydroxy cyclooctanes, and thus, resorcinol or resorcinol monoacetate, pyrogallol diacetate, etc., and the corresponding propionates, butyrates, caproates,

etc., may be reacted with the chloroformates of are solids. The new unsaturated compounds are usually miscible with solvents such as benzene, toluene, chloroform, diethyl ether, carbon tetrachloride, and petroleum ether. The monomeric ene, or carbon tetrachloride. Upon further polymerization, theliquid sets up to form a soft gel containing a substantial portion of a polymer which is insoluble in the monomer and organic solvents and containing as well, a substantial portion of a soluble material which may be monomer and/or soluble fusible polymer. These gels are softv and bend readily. However, they are fragile and crumble or tear under low stresses. They may be further polymerized in the presence of catalysts to the final infusible insoluble state in which substantially all of the polymer is substantially infusible and substantially insoluble in organic solvents, acids, and alkalies.

*The monomers of the polyunsaturated esters may be cast polymerized directly to the substantially insoluble, infusible state. This .procedure is subject to certain inherent difliculties due to esters are valuble as plasticizers for various resin materials such as styrene, cellulose, vinyl, urea, pr0tein,. phenolic, or acrylic resins. Other uses such as solvents, insecticides, and liquid coatin compositions are noteworthy.

These esters may be polymerized in the presence of heat, light, or catalysts such as oxygen,

ozone, or organic peroxides such as lauroyl, benzoyl, and acetone peroxides, to yield solid or liquid compositions of widely differing physical properties. The polymerizedproducts vary in properties depending upon the structure of the ester and upon the degree of polymerization.

The polyunsaturated esters contain at least two radicals derived from unsaturated alcohol and are capable of polymerization to a fusible intermediate stage and finally to a substantially infusible and/or insoluble form. The completely;

polymerizedpolyunsaturated compounds are, in general, substantially unaffected by acids, alkalies, water, and organic solvents. Intermediate polymers derived from the polyunsaturated esters having a wide range of properties may be secured by incomplete polymerization. The polymers thus obtained are transparent and colorless, although they may at times have a slightly yellow cast, especially when polymerized completely. Many of these new polymers are generally tougher and more resistant to shattering than are the unsaturated alcohol esters of polybasic acids.

Upon the initial polymerization of the polyunsaturated esters inliquid monomeric state or in a solution of the monomer in suitable solvents, an increase in the viscosity'of the liquids is noticeable due to the formation of a simple polymer which is soluble in the monomer and in solvents the strains which are established during polymerization of the gel and which frequently result in fractures as the final hard form is attained. It has been discovered that these difliculties may be avoided by releasing the strains established in the gel before the fracturing can occur. This may be done by permitting the strains to be relieved before the polymerization is complete, ither periodically or by conducting the polymerization under conditions which permit gradual release of these strains. For example, the polymerization may be conducted in a simple mold until a soft firm gel has formed. At this point the polymer may be freed from the mold to which it adheres strongly. When released this polymer contracts substantially, thereby relieving the I polymerization strains. The gel may thereafter be shaped, if desired, and polymerized to the final infusible state. Smooth, optically perfect sheets may be made by this method. Preferably, the initial polymerization is conducted at a temperature sufliciently low to prevent the complete decomposition of the peroxide catalyst. This temperature is dependent upon the catalyst used. For benzoyl peroxide,-temperatures of 65 to C. are suitable while for acetone peroxide, temperatures of 140-150? C. may be used. In accordance with one modification, the gel, after it is freed from the mold, maybe coated on both sides with monomer or the syrupy polymer. The coated article is then polymerized between smooth heated plates to the final insoluble state.

In order to inhibit formation of cracks dur g the initial polymerization, it is frequently desirable to minimize the polymerization on one side This is-done by conducting the polymerization with one side exposed to the air which inhibits polymerization in the presence of a peroxide catalyst, such as benzoyl peroxide.'

Thus, a sheet is produced which is hard and smooth on one side while being soft and tacky on the other. The sheet may thenbe finished by coating the tacky side with monomer or syrupy polymer and polymerizing it in contact with a smooth plate'to the insoluble, infusible state. Often it is found desirable to release the polymer from the plate one or more times during polymerization of the coating in order' to minimize formation of cracks or other surface defects.

Cast polymers may also be prepared by a single step polymerization directly to the insoluble infusible state. The monomer may be mixed with one to five percent of benzoylor other organic peroxide and heated at 50-60" C. until it becomes partly polymerized and thickened to an increased viscosity of to 1000 percent of the monomer viscosity. The thickened monomer may thenbe polymerized between glass, metal, or similar plates which are separated by compressible gaskets or retainers of Koroseal (plasticized polyvinyl chloride), butadlene polymers, polyvinyl alcohol, Thiokol (polyethylene sulfide), rubber, or similar materials arranged about the edge ofsuch plates. The thickened monomer may be poured on one lass plate within the confines-ofthe flexible retainer, laid .about 2 inches from the edge of the plate. The second glass plate then may becarefully laid on top taking care to avoid the trapping of air bubbles under the top plate. When the top-plate is in position, both plates may be held. together by means of suitable clamps which are capable of applying pressure upon the plates and are placed directly over the flexible retainer. The 'entire assembly is then placed in an oven and heated at 70 to 100 C. where the polymerization is continued. During the polymerization the resin shrinks and tends to draw away from the glass surfaces. To prevent fractures, pressure is maintained upon the plates to depress the flexible container and permit the plates to remain in contact with the polymerizing resin. This pressure may be maintained by periodically'tightening the clamps or by use of spring clamps-which maintain a uniform pressure throughout the polymerization process.

By an alternative procedure for east polymerizing sheets, the molds may be assembled before the thickened monomer is poured. Thus, the flexible compressible retainer may be inserted between the plates and held in place by suitable clamps located around the edge of the plates. This retainer or gasket is placed adjacent the edge of the plates and a suitable opening may be provided between the ends of the flexible retainer, preferably at one corner of the mold. The assembled mold is then placed in a vertical position with the open corner uppermost. The thickened monomer containing one to four percent residual peroxide is then poured in slowly until the entire mold is filled. After standing until all of the entrapped air has separated the mold is heated uniformly between 70 and 100 C. to con-' tinue the polymerization. Pressure is maintained upon the plates to insure the contact of glass and resin during polymerization by suitable means such as by tightening the clamps periodically or by maintaininga uniform pressure upon the plates throughout by means of spring clamps.

aaeaose obtained in stable solid form and as such may beuscd as a molding powder or may be redis-. solved in suitable solvent for use'in liquid form. It is soluble in organic solvents which are normally capable of dissolving methyl methacrylate polymer or similar vinyl type polymer, Preferably, the fusible polymers of the new unsanirated esters are produced by heating the monomer or a solution thereof in the presence of substantial quantities, for example, 2 to 5 percent of benzoyl' peroxideuntil the. viscosity of the solution has increased about 100 to 500 percent. This may require from one-halfvv to two hours while heating at 65 to 85 C., in the presence of henzoylperoxide. The resulting viscous solution is pouredlnto an equal volume'of water, methyl or ethyl alcohols, glycol or other nonsolvent 'for the fusible polymer. A polymer usually in the :form of a powder or a gummy precipitate is thus formed which may be filtered and dried. This permits substantially complete separation of a soluble fusible polymer from unpolymerized monomer.

Often, however, such complete separation is not desirable since hazy products may be secured upon further polymerization. Accordingly, it is often desirable to produce compositions comprising the fusible polymerand the monomer. This When the resin has been completely polymerized merization may be suspended while the monomer-polymer mixture is in the liquid state and before the polymer is converted to a gel by cool-. ing, removal from exposure to ultraviolet light,

' by adding inhibitin materials such as pyrogal lol, hydroquinone, aniline, phenylene diamine, or sulphur, or by destruction of the polymerization catalyst. The fusible polymer may be separated from all or part of the monomer by any of several methods. It may be precipitated by the addition of nonsolvents forthe fusible polymer such as water, ethyl alcohol, methyl alcohol, or glycol. Alternatively, it may also be separated from the monomer by distillation in the presence of an inhibitor for polymerization and preferably at reduced pressures. The fusible polymer is thus may be effected by partial distillation or extraction of monomer from the polymer or by reblend ing a portion of the fusible polymer with the same or a different polymerizable monomer. In general, the composition should contain at least 40 percent'and preferably in excess of 50 percent fusible polymer and from about 5 percent to 50 or 60 percent monomer.

Preferably, the production of these materials is conducted by treatment, of a solution of the monomer in a solvent for monomer and polymer such as benzene, xylene, toluene, carbon tetrachloride, acetone, or other solvent which normally dissolves vinyl polymers.

Other polymerization methods may involve the interruption of the polymerization while the polymer is a gel. For example, a soft solid gel containing a substantial portion of fusible polymer may be digested with a quantity of solvent for the fusible polymer to extract the fusible gel from the infusible. The solution may then be treated as above described to separate the fusible polymer from the solvent. These polymers may be used as molding or coating compositions. Due to their solubility, they are particularly desirable for use in paint compositions.

Other fusible polymers may be prepared by carrying the initial polymerization to the point where the polymer is in the form of a gel which generally contains at least20v percent and preferably about 45 to 80 percent by weight of substantially insoluble polymer, but at which point the gel is still fusible. This solid resin composition may be disintegrated to a pulverulent form and used as a molding powder. Alternatively, a

desirable polymer maybe prepared by emulsifyq ing compositions.

dispersion of fusible polymer in monomer or other fuses or blends together to form a substantially homogeneous product beiore the composition is polymerized to a substantially infusible state. This may be eifected by conducting polymerization at an elevated temperature and/or presssure der may be copolymerlzed with phenolic, cellulose acetate, urea, vinylic, protein, oracrylic resins. It is thus possible to produce transparent or opaquev forms of a wide variety of colors and hardnesses, depending upon the proper selection of the modifyin agents. I

fusible polymers may be dissolved in suitable solvents and used as coating and impregnat- For example, the solution or organic solvent such as benzene, toluene, chloroform, phenyl cellosolve, dichlorethyl ether, dibutyl phthalate, or mixtures thereof, is useful as a liquid coating composition. Objects of paper, metal, cloth, wood, leather or synthetic resins mayfbe coated with the solution of polymer in "in single layers orlaminated may be impregnated with the dissolved fusible polymer and subjected to the polymerization to the final insoluble infusible state.

. Other molding powders maybe prepared from the-new esters without first converting them to the soluble intermediate polymer. For example, the monomer may be mixed directly with a suitable filler such as magnesium carbonate, cellulose pulp, asbestos, etc., in a ball mill or other mixing device. By proper selection of proportions a dry pulverulent powder can be obtained which is capable of polymerization under the influence of heat andpressure to a glossy solid polymer oi high tensile strength. The use of too much filler will'cause a non-glossy finish and the use of too much monomer will make the powder moist and difigult to handle. Sometimes it may be desirable, to precure the molding powder by subjecting it to. a nioderate temperature, 50 to 70 C., for a lim-" ited period of time, for example, one to three hours. This precuring operating is a partial poly. merization and permits formation of a drying molding powder where the same proportion of monomer might result in a moist molding com: position.

Further details of the synthesis of these new I esters and of their applications will be apparen from the following examples:

I Example! Allyl chloroformate was prepared by placing 500 cc. of allyl alcohol in a flask equipp d with gene had been added the reaction was discontinned and thecrude material was permitted to stand at room temperature to separate the excess phosgene. The reaction mixture was washed with water to remove the excess allyl alcohol and the allyl cmoroi'ormate =was-distilled in vacuum '(b. p. 46-51 at 80 mm.)

One mol' (120 gms.) of allylehloroiormate was added slowly to 53 ms. of 'diethylene glycol, and 100 of pyridine. The chloroformate addition required about one-half hour during which time the reaction mass was maintained between +5 and +15 C. The resulting mixture ,was washed with dilute HCl and with water and purified by distillation in a vacuum. The resultheated at 50 c. m a solution 01-200 cc. of car-' bon tetrachloride with 2 percent benzoyl peroxide cent. 500 cc. of methyl alcohoLwere added and a gummy polymer was precipitated. After filteracetone, dioxane, carbon tetrachloride,

. solvent and subsequently polymerized to yield at.

Similarly, porous ing and drying, a 5 gm. sample of the soft polymer was mixed with 5 percent benzoyl peroxide and pressed in a mold at a pressure of- 2000 lbs. per sq. in. at a temperature of 150" C. A hard, colorless, transparent polymer was produced.

Example 11 i Methallyl chloroformate was prepared by passing 'phosgene into 500 cc. of methallyl alcohol at a rate of 50-65 millimoles per minute. The mass was stirred throughout the reaction and 'main tained at a temperature between 5 C. and 10 C.

.means of an ice bath. The

by means of an ice bath. When approximately an equimolar quantity of phosgene had been absorbed the reaction was stopped and the product was washed with dilute hydrochloricacid and. salt solution (NaCl).

The methallyl chloroformate was distilled at 126-136" C. (760 mm.). 134 gms. of the chloroformate was .added dropwise to 31 gms. of ethylene glycol and an excess gms.) of pyridine. The temperature was maintained below +10 C. during the reaction by (methallylcarbonate) V CHFC-CHI-O-C-O H8 or! CH: 0 H! was distilled at 146 c. (2 mm). It has an index for 2 hours. The viscosity had increased appre ciably but themass was still liquid. A half-liter of methyl alcohol was added to precipitate the fusible polymer which was filtered and dried. The

. polymer was a soft gummy material and after drying it was a non-viscous granular solid.

A five gram sample was mixed with five percent benzoyl peroxide and pressed in a mold at 150 C.

and 2000 pounds per square inch pressure. A

colorless, transparent solid polymer was formed.

I Example III 7.2 moles of allyl chloroformate was added dropwise to a solution of 2 moles of glycerine in 7.8 moles of pyridine while cooling the reaction ethylene glycol bis about 45 minutes.

assaesafraction or about (1%") 1.444s, a density on) mixture to a temperature or. 10 m 15 0. After the chloroformate had been added, the mixture was alio ed to stand at room temperature for g V m-o-tLo omon=om Example IV A sample of 120 gms. or methyl glycerine and 500 cc. of benzene were placed in a 2000 cc. flask with 250 gms. of pyridine. Whilethe mixture thus secured was a colorless liquid which had was being stirred, 350 gms. of methallyl cloroformate was added at a rate sufllciently slow to prevent the temperature from rising about 50 C.;

When the addition was completed the water j layer was separated and the oil layer was washed with dilute H01 and with water. The carbon tetrachloride was evaporated by heating at 50-60 mm. total pressure.

and heated at 50 C. Atthe end of three hours the viscous solution was poured into 1000 cc. of

- methyl alcohol and a large quantity of a gelat inous polymer was precipitated. I

A five-gram sample of the dried polymer was mixed with five percent benz'oyl peroxide; It was heated (160 C.) in a mold under 1500 pounds I per square inch pressure. A hard, translucent and nearly colorless solid was produced. The monomer had the following structure:

Phosgene was bubbled into a flask containing allyl alcohol at a rate or 20 millimoles per minute while agitating the mixture and cooling to atem-' perature below about to C. After phosgene in the proportion of about 0.9 moles of phosgene per mole of allyl alcohol had been introduced, the mixture was allowed to stand for one hour. Thereafter, the reaction mixture was washedwith water to remove unreacted'allyl alcohol and dried over calcium chloride.

2.2 moles of allyl chloroformate was added dropwise to a solution of one mole of ethylene glycol in 2.4 moles of pyridine while cooling'the reaction mixture to a temperature 01 10 to 15 C. After the chloroformate had been added, the mix.. ture was allowed to stand at room'temperature for about one hour. The product was diluted with water, washed with dilute HCl solution and then with sodium chloride solution unti neutral. Thereafter, the product was washed with water and dried over calcium chloride. The ethylene glycol bis (allyl carbonate) having a boiling point of about 118-122 C. at 1 mm., an index of re- The ester was mixed with 500 cc. benzoyl and 5 grams benzoyl peroxide I was obtained 1 about 1.114, and having the probable formula: ononomo-c-o cn,cH,o-c-o-cn,on=cn,

. Example VI Theprocess described in Example V was reeated using an equivalent amount or tetraethyiene glycol in lieu of ethylene-glycol. The ester an index of refraction (N of about 1.454, a density of 1.133 at C. Polymerization oi' the material occured when distillation was attempted at 2 mm. pressure.

Example VII The process described in Example V was peated using an equivalent amount or diethylene glycol in lieu of ethylene glycol. The ester thus obtained was a colorless liquid which had an index of refraction of 1.449 at 20 C., a density of about 1.133 at 20 C./4 C. and a bolling point of about 166 C. at 2 mm. pressure.

by heating with aboutten times its weight of pyridine for 16 hours at 85 C. The solution was cooled to about 0 C. and mixed with cold ailyl chloroformate while maintaining the temperature at 5 to 7 C. The mixture was stirred, warmed to 40 C. and poured into water slightly acidified with hydrochloric acid. A white sticky gum was precipitated.-- This gum was dissolved,

reprecipitated with water from acetone solution and a tough, white polymer was obtained. This product cured to an infusible, insoluble state upon heating with 5' percent benzoyl peroxide.

Example IX Pentaerythritol tetrakis (methallyl carbonate) was prepared by treating 100 gm. of pentaerythritol with 4'75 gms. of methallyl chloroformate in the presence of 302 gms. of pyridine. The reaction was conducted at temperatures between 5 and 15 C. by adding the chloroformate slowly to a mixture of the other reagents. When the reaction was completed the mixture was per hard transparent solid by heating to 140 C. with 3. percent benzoyl' peroxide. The monomer has the following structure:

with 200 cc. of'dioxaneand treated with an excess of phosgene. at a temperature between, 5 and '+5 C.,-by cooling with an acetone-dry ice;niixture'. The tetrachloroformate of erythritol was produced and separated from the dioxane, by

, I I Examplel'll! I A quantity or polyvinyl alcohol was dissolved heating lna vacuum. The chloroiormate was then treated with 100 gms. of allyl alcohol and .150 gms. of pyridine at a temperature between and 15 C. as in previous examples. The ester was washed with dilute HCl and with dilute NazCOz. A flve gram sample was heated with 5 percent benzoyl peroxide and a hard, brittle translucent solid was produced.

I Example XI One-halt mole o1 resorcinol (55 gms.), 80 gms. of pyridine and 200 cc of dioxane were placed in a one-liter flask equipped with a continuous stirrer and provided. with an ice bath. 120 gms of allyl chloroformate were added over a" period of one hour. The addition. was begun at a very slow rate and speeded up toward the end of the reaction to maintain the temperature oi the reactants between +5 and 15 C. The mixture was 1 washed with water and heated under reduced pressure to evaporate the solvent. The unsaturated ester was believed to have the following structure:

A ten gram sample was heated with 3 percent benzoyl peroxide for 1 hours to produce a polymer.

Example XII with water to remove the excess alcohol. The

product was a solution of the ester:

CHI

I o-i -ocm-c hcni in carbon tetrachloride.

A quantity of lauroyl peroxide (2 percent based on the theoretical yield of the ester) was added and the mixture was heated at 50 C. for four hours. The viscous solution was poured into 1000 cc. of methyl alcohol and a substantial quantity of soft gummy polymer was precipitated. The polymer was separated and dried.

A ten gram sample of the fusible polymer with 5 percent benzoyl peroxide was pressed in a mold at 125 C. for an hour. A hard brittle polymer was produced. 7

Example XI]! One mole (126 gms.) oipyrogallol was dissolved in 300 cc. of carbon tetrachloride. To this solution 250 gm. of pyridine was then added. Three moles of allyl chloroiormate were slowly added to the mixture while stirring vigorously. The reaction mass was maintained below 20 C. by cooling on an \ice bath. When the reaction was completed the mixture was washed with very dilute HCl and water. '-The solvent was removed asaaesa was produced insubstantial quantities.

A five gram sample or the crude ester was heated to C. for 2 hours with 5 percent acetone peroxide. A viscous polymer was produced.

Example XIV The precedure of Example XII was repeated using catechol in place of resorcinol. The following ester was produced:

('33: H: A ten gram sample was heated at 75 C. for 2 hours to form a slightly yellowish polymer.

' Example XV 200 grams of the monomer produced in Example I was mixed with 5 percent benzoyl peroxide and heated at 60C. for 3 hours. The ester increased in viscosity to about 600 perc-entof the normal monomer viscosity.

A mold was prepared with two sheets of polished plate glass (15" x 15") separated about A" with a /2" x A" x 54" strip of soft flexible Thiokol. The flexible retainer was located about one inch from the edges of the glass and held in place by clamps placed 3" apart around the periphery of the assembly. The ends of the flexible strip were about 2 inches apart at one corner.

The mold was placed in a vertical position and filled with thickened monomer, through the opened corner. After standing for. 15 minutes to permit the separation of entrapped air bubbles, the filled mold was placed in an oven and heated for 4 hours at 70 C. The clamps were then tightened to restore the pressure lost due to the shrinkage and the heating continued for 2 hours after which the clamps were again tightened. After 8 and 10 hours total lapsed time the tightening procedure was repeated. The mold was removed at the end of 12 hours and the glass plates separated; A transparent sheet of polymer having polished'surfaces and high tensile strength was produced.

Although the present invention has been described with respect to certain specific modifications, it is not intended that the details of such modifications shall be limitations upon the invention except as incorporated in the following claims.

We claim:

1. Resorcinol bis (allyl carbonate).

2. Catechol bis (methallyl carbonate).

3. A polymer-of resorcinol bis (allyl carbonate).

4. A polymer of catechol bis (methallyl carbonate) 5. An ester having the following structural forasseuse 7 wherein a; la a radical equivalent to the radical 'l. The compound of claim 5 wherein R1 is R1 in the alcohol RiOH, said alcohol being a the methallyl radical.

' monohydric, unsaturated aliphatic alcohol con,- 8. The compound of claim 5 wherein R1 is the taming from 3 to 10 carbon atoms and hav- 2-"chloroallyl radical.

Y in; an unsaturated carbon-to-carbon linkage be- 5 9. A polymer of the compound of claim 5.

tween the beta and gamma carbon'atoms therein, a

and a: is a small whole number greaterthan one IRVING E. MUBKAT.

and less than four. FRANKLIN STRAIN.

6. The compound or claim 5 wherein R1 is the allyl radical. l0 

